title: Infrared Studies on Bimetallic Copper/Nickel Catalysts Supported on Zirconia and Ceria/Zirconia.
abstract: Infrared spectroscopy has been employed for a detailed characterization of ZrO2and CeO2/ZrO2supported nickel and copper/nickel catalysts to be utilized for methane decomposition. Adsorption of CO at 303 K was performed in order to determine the surface composition and accessible adsorption sites. Alloy formation occurred during reduction, as indicated by a red-shift of the vibrational band of CO on Ni: by 27 cm-1on nickel-rich CuNi alloy, by 34 cm-1on 1:1 Cu:Ni and by 36 cm-1on copper-rich CuNi alloy. CuNi alloy formation was confirmed by X-ray absorption spectroscopy during reduction revealing a considerably lower reduction temperature of NiO in the bimetallic catalyst compared to the monometallic one. However, hydrogen chemisorption indicated that after reduction at 673 K copper was enriched at the surface of the all bimetallic catalysts, in agreement with IR spectra of adsorbed CO. In situ IR studies of methane decomposition at 773 K demonstrated that the addition of Cu to Ni strongly reduced coking occurring preferentially on nickel, while maintaining methane activation. Modification of the zirconia by ceria did not have much effect on the adsorption and reaction properties. Ceria-zirconia and zirconia supported samples exhibited very similar properties and surface chemistry. The main difference was an additional IR band of CO adsorbed on metallic copper pointing to an interaction of part of the Cu with the ceria.
authors.affiliation: Institute of Materials Chemistry, Vienna University of Technology, Getreidemarkt 9 BC01, 1060 Vienna, Austria.
authors.forename: Astrid
authors.initials: A
authors.lastname: Kitla
authors.forename: Olga V
authors.initials: OV
authors.lastname: Safonova
authors.forename: Karin
authors.initials: K
authors.lastname: Föttinger
keywords: Bimetallic catalyst; CO adsorption; Coke; CuNi alloy; Infrared spectroscopy; Methane conversion